Lambda Arietis is a double star in the constellation Aries and is best viewed during the winter months. From a dark sky location, Lambda will appear as a faint star with the naked eye. Look through a telescope, and that pinpoint of light splits into a colorful double due to the strong contrast between the stars.
Lambda A, the primary bright star, is cataloged as yellow-white, while the fainter Lambda B is a cooler and warmer yellow. In the eyepiece, however, observers have witnessed various colors, from silvery white for both stars all the way to yellow and blue. See my observation below as the Lambda B appears green to me, close to how writer Greg Stone sees the star. 1
Lambda A and B are separated by a healthy 30 arcseconds in the sky, so a smaller telescope under good conditions should split this pair nicely. The stars lie around 130 light years way from earth and are 1,500 Astronomical Units apart. For those unware, one Astronomical Unit is 93 million miles or the distance from the earth to the sun.
My Observations
| Date | January 27, 2022 |
| Time | 7:45 p.m. |
| Location | Seattle, WA |
| Magnification | 145x |
| Scope | Meade 8″ SCT |
| Eyepiece | 14mm |
| Seeing | Above Average |
| Transparency | Above Average |
Lambda Arietis is becoming one of my favorite double stars! I know a star technically cannot be green, but on this evening, this pair is a warm yellow (almost pinkish) and a pale green. It’s like finding a darker yellow topaz sitting in a treasure chest right beside a lighter emerald.
Key Stats
| Constellation | Aries |
| Best Viewing | Winter |
| Visual Magnitude | +4.8 | +6.7 |
| Absolute Visual Magnitude | +1.8 |
| Separation | 37″ |
| Position Angle | 48° |
| Distance from Earth | 130 ly |
| Orbital Period | 33,000+ yrs |
| Milky Way Location | Orion Spur |
| My Viewing Grade | A- |
| Designations | 9 Ari, HD 11973, SAO 75051, HIP 9153 |
Sources and Notes
Banner adapted from an illustration created by Pablo Budassi. The illustration is licensed under the Creative Commons Attribution-Share Alike 4.0 International license. Full details here.
1 Lambda (λ) arietis, 1 arietis – and a whole new way of staying warm. Star-Splitters. (2010, December 13). Retrieved May 15, 2022, from https://bestdoubles.wordpress.com/2010/12/11/lambda-%ce%bb-arietis-1-arietis-and-a-whole-new-way-of-staying-warm/
Sketch by Wayne McGraw
The Garden Astronomer 